Tents are used by firefighting personnel near forest fires, to create command and control centers and to treat the wounded. If climate control is needed, portable air conditioning units and/or oil-based heating units are separately coupled to tents. Tents are also used to establish command and control and medical facilities by the military near battlefields.
It has also been proposed to use tents and other portable structures that may be quickly assembled in medical emergencies to house patients, as well as medical and command and control personnel. For example, hospital capacity may need to be increased to handle patients from a large accident, an epidemic, or a natural disaster. Portable medical facilities may also need to be quickly assembled at or near a site of a medical emergency, such as a fire, or a chemical, biological, or a nuclear accident or incident, such as a terrorist attack.
Temperatures may vary widely across regions and in the same location during different times of the year and different times of the day. Temperature variations over 80% of the United States and other temperate regions lie within the range of from about 0° F. (−18° C.) to about 100° F. (38° C.). Typical temperature variations over climate extremes from the arctic to the desert lie within the range of from about −20° F. (−11° C.) to about 120° F. (48° C.). The temperature variation in a single location may vary from 100° F. (38° C.) in the summer to 0° F. (−18° C.) in the winter. The temperature variation in a location may also vary from 80° F. (27° C.) during the day to 50° F. (18° C.) at night, for example, at certain times of the year. Cooling may therefore be required during the day while heating is required at night.
An optimum temperature range for comfort is between about 68° F. and 72° F. (about 20° C. and 22° C.), for example. Since the optimum temperature range is closer to the upper end of the above temperature ranges than to the lower end, cooling is required over a smaller portion of the ranges than heating. In the summer, for example, cooling could be required for up to about 30 Fahrenheit degrees (17 centigrade degrees) (from 100° F. (38° C.) to 70° F. (21° C.), for example) in a temperate climate. In the winter, in contrast, heating may be required up to about 70 Fahrenheit degrees (39 Centigrade degrees) (from 0° F. (−18° C.) to 70° F. (21° C.), for example). Heating a tent in certain locations may therefore require about twice as many BTUs of heat as BTUs of cooling to cool the tent.
Air conditioning units typically comprise an evaporator, a condensor, and a compressor. Refrigerant fluid for cooling flows through coils in the evaporator. A fan moves air to be cooled through the evaporator, over the coils. The fluid absorbs heat from the air, which cools the air and vaporizes the refrigerant fluid. The vaporized fluid is pumped to the condensor by the compressor. In the condensor, which also comprises coils, the vapor condenses, releasing the heat to air or other such medium flowing through the condensor, removing the heat from the unit. The refrigerant is then pumped back to the evaporator.
FIGS. 1a-1c are schematic representations of three types of standard evaporators: 1) an up flow V-shaped evaporator 10; 2) a horizontal flow evaporator 20; and 3) a window-type evaporator 30. The evaporators comprise coils 50. Due to their low temperature, moisture 40 condenses on the evaporator coils 50. The moisture is forced off of the coils 12 by the air flow F and drips or runs down the outside of the evaporator into drip pans 60, due to the force of gravity. The V-shaped evaporator 10 and the horizontal flow evaporator 20 are angled with respect to the air flow F, to facilitate drainage. The face of the window-type evaporator 30 is normal to the air flow F. Air flow F through these evaporators 10, 20, 30 is uniform across the face of the evaporator, and across the coils 50.